Field of the Invention
This invention relates in general to the field of building energy management systems (BEMSs), and more particularly to technique that provides for automatic power metering at the device level.
Description of the Related Art
The problem with resources such as electrical power, water, fossil fuels, and their derivatives (e.g., natural gas) is that the generation and consumption of a resource both vary with respect to time. In addition, the delivery and transport infrastructure limits instantaneous matching of generation and consumption. These resources are limited in supply and the demand for this limited supply is constantly fluctuating. As anyone who has participated in a rolling blackout will agree, the times are more and more frequent when resource consumers are forced to face the realities of limited resource supply.
Most notably, the electrical power generation and distribution industry has taken proactive measures to protect limited instantaneous supplies of electrical power by imposing financial disincentives such as peak demand charges and time-of-use (TOU) pricing for the creation of high peak demand and the consumption of electricity during peak demand periods. Heretofore, consumers merely paid for the total amount of power that they consumed over a billing period. Today most energy suppliers not only charge customers for the total amount of electricity they consume over the billing period, but they additionally bill the customers for their peak demand reading, that is, the greatest amount of energy that is used during a measured period of time. Additionally, energy suppliers are beginning to charge higher rates for power consumed during peak demand periods with mechanisms such as time-of-use pricing.
For example, consider a factory owner whose building includes 2,000 fluorescent light fixtures, each consuming 100 Watts when fully on. If all the fixtures are on at full power during the measuring period, then the peak demand for that period is 200 KW. Not only does the energy supplier have to provide for instantaneous generation of this power in conjunction with loads exhibited by its other consumers, but the distribution network that supplies this peak power must be sized such that it delivers 200 KW to the factory. Consequently, it is standard practice today that customers that create high peak demand and consume electricity during peak demand periods are required to pay a surcharge to offset the costs of peak energy generation and distribution.
In addition to financial disincentives for contributing to peak demand, many utilities (e.g., Pacific Gas & Electric) offer financial incentives to customers to actively reduce peak and overall demand through participation in so called demand response and energy efficiency programs, as well as to upgrade to more efficient and controllable building equipment. In demand response programs, utilities pay incentives for reducing demand “on-call” during peak demand periods such as hot summer afternoons. In energy efficiency programs, utilities pay incentives for making their building more efficient, thereby consuming less electricity overall. This process often includes building energy audits, upgrades to more efficient equipment (e.g., heating, ventilation, and air conditioning (HVAC); lighting; etc.), and the installation of building controls and energy management systems. Since, building owners, among others, are not necessarily trained or equipped to fully exploit the savings opportunities offered by the utilities, an entire industry of intermediaries has developed to provide the knowledge, equipment, service, and capital necessary to participate in demand response and energy efficiency programs, as well as to make their buildings more efficient with new equipment and controls. These intermediaries, or Energy Management Companies (EMCs), include demand management service providers like ENERNOC, INC.®, energy service companies (ESCOs) like AMERESCO®, and others. Demand management service companies enable participation in demand response programs, they monitor and manage peak demand creation, they optimize consumption in light of time-of-use pricing, as well as performing other services. Overall, they seek to save the customer more than the demand management service costs. ESCOs install new, more efficient HVAC and lighting equipment in facilities. The also own the equipment for a period of time, thus earning payback and profit on their investment through the savings that they create. All EMCs seek to leverage incentives from utilities in order to improve the value they offer their customers and to increase their returns. In order to prove the value that they have created, both to the customer and to the utility, EMCs are often burdened with the obligation of “measurement and verification” (M&V) of reduced demand or efficiency created.
As a standard practice, ESCOs generally own the new equipment they install (at no cost to the building owner) in the building for seven to 10 years, and contract with the building owner to produce a specified amount of efficiency, which results in a lower utility bill. These “savings” are the difference between what the bill would have been without the efficiency measures and what the new, lower bill is with them in place. During the performance period, the ESCO is paid the bulk of the savings created and the remainder accrues to the building owner. The ESCO generally achieves payback inside of 75 percent of the performance period and profits until conclusion. The building owner has a slightly lower utility bill during the performance period and a much lower utility bill afterwards, in addition to owning a more efficient building with new equipment with no cash outlay. In essence, an ESCO guarantees performance to the building owner while assuming the risk of underperformance. However, in order to create a performance contract with the building owner, ESCOs must be able to prove the efficiency that they create. In the past, ESCOs have limited their activities to the simple replacement of inefficient equipment with equipment that consumes less electricity. For example, an ESCO might replace existing T12 fluorescent lamps and ballasts with more efficient T8 lamps and ballasts. In this case, the efficiency created is known on the front end of the project and no measurement and verification during the project is necessary.
The present inventors have observed that substantial energy savings can be obtained through the employment of lighting control systems that include such devices as dimmable lighting electronics (e.g., fluorescent ballasts, LED drivers), daylight harvesters, and occupancy sensors. Lighting control systems achieve efficiencies of 60-80 percent by actively modifying the lighting levels according to need (e.g., dimming or turning off lamps when a room is not occupied, leveraging ambient light entering the building through windows and skylights by dimming lighting to only what is necessary to achieve suitable overall lighting levels, etc.). What is precluding ESCOs and others from implementing these control systems in a performance contracting model is the fact that they are inherently dynamic in nature, and actual efficiency created is dependant on more variables than simply installing more efficient electronics. Thus, the present inventors have noted that ESCOs need a cost-effective and accurate method of measuring and verifying efficiency created in dynamic control systems such as a lighting control system. Furthermore, the present inventors have noted that it is virtually impossible to measure lighting energy use only at the meter or circuit breaker level, due to the “noise” created by many other electrical loads in the building. These factors act as disincentives for ESCOs to install dynamic lighting control systems.
Consequently, the problem of measuring and verifying actual efficiency created by dynamic control systems extends beyond lighting to HVAC systems, motors, and other electrical loads.
Utilities require by contract that demand management service providers measure and verify curtailed load during demand response events in order to be paid for the service. Heretofore, the majority of electrical loads employed in demand response programs has been large industrial loads that customers are willing to shut down during a demand response event. These large loads have known electrical footprints and their curtailment can easily be measured and verified at the meter with a common power meter. Much attention has been given by utilities and EMCs to extend demand response programs beyond the industrial context into commercial buildings using lighting and HVAC as the curtailable load. To date, this has occurred in a very small percentage of commercial buildings. In order to effectively control loads such as lighting and HVAC that owners and tenants of building depend upon for quality of service, dynamic control systems such as are noted above are often employed, making it difficult or prohibitively expensive to measure and verify the load curtailed during an event. This has limited the deployment of demand response programs in commercial buildings.
Utilities and industry players have promoted and developed the Open Automated Demand Response (OpenADR) standard that defines a communication protocol between utilities and automated infrastructure in commercial buildings for demand response purposes. According to OpenADR, utilities communicate demand response events to intelligent energy management systems in commercial buildings, which acknowledge receipt of the event notification. However, the utility has no insight into how much curtailable load exists prior to the event nor the actual amount of load curtailed building by building during or after the event. This is primarily because no technology exists in commercial buildings to cost effectively measure power consumption at the device level. And the present inventors have noted that with such technology, an energy management system could compare current consumption levels with demand response tolerance profiles established by the building owner, device by device, and advertise to the utility in real-time the demand response “capacity” of the building. This would dramatically improve the effectiveness of OpenADR programs and improve the efficiency of the utility's grid.
The present inventors have also noted that demand management service providers can reduce building owner utility bills by monitoring and limiting peak energy consumption of the building. The ability to perform this service is greatly enhanced by the ability to cost-effectively measure power at the device level, particularly in the context of dynamic control systems. By understanding power consumption at the device level and in aggregate for the building, the service provider can adjust and curtail discretionary loads temporarily in real-time, thereby avoiding unnecessary and costly artificial peak consumption.
The present inventors further note that demand management service providers can further reduce building owner utility bills by adjusting and timing consumption according to variable time-of-use rate structures that are increasing employed by utilities. Again, the ability to perform this service is greatly enhanced by the ability to cost-effectively measure power at the device level. Some loads are more discretionary than others (e.g., lowered lighting levels are generally more tolerable than increased temperatures), and understanding the power consumption and real-time cost at the device level increases the effectiveness of the service.
Many utilities subsidize the creation of more efficient buildings by paying incentives for the installation of more efficient lighting and HVAC equipment. While the value of more efficient equipment is well understood and incentives can be sized appropriately, the present inventors note that the value of dynamic control systems as described above is less so. For the same reasons that ESCOs are hesitant to install dynamic control systems, utilities are hesitant to pay blindly for incentives for dynamic control systems. However, the present inventors have observed that with the ability to cost-effectively measure power at the device level, utilities would be able to size incentives based upon real-world measurements of efficiency created once the system was installed. The lack of such technology limits the growth of energy efficiency programs and the dissemination of highly efficient dynamic control systems.
Therefore, what is needed is a cost effective mechanism for measuring power consumption at the device level (e.g. fluorescent ballast, LED driver, HVAC equipment, power supplies, etc.).
What is additionally needed is an apparatus for automatic power metering that utilizes existing access points in common original equipment manufacturer (OEM) device electronics (e.g. fluorescent ballast, LED driver, HVAC equipment, power supplies, etc.) to obtain sub-metering data.
What is further needed is a low cost technique for implementing power metering at the device level, which operates in conjunction with existing power factor correction circuitry.